Ocymyrmex cursor

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Ocymyrmex cursor
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Ocymyrmex
Species: O. cursor
Binomial name
Ocymyrmex cursor
Bolton, 1981

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Specimen Labels

Nothing is known about the biology of Ocymyrmex cursor.

Identification

A member of the laticeps group

Bolton (1981) - The closest relative of cursor is Ocymyrmex laticeps, also from Angola.

laticeps - Smaller species, HW 1.70-1.74, SL 1.56, PW 1.08-1.14. Head slightly broader than long, CI 102-103. Metapleural lobes vestigial, scarcely or not visible in absolute profile. Anterior half of propodeal dorsum sloping downwards, posterior half more or less level. Petiole node in profile with a short, narrowly rounded dorsum. Postpetiole longer than broad in dorsal view.

cursor - Larger species, HW 2.04, SL 1.94, PW 1.30. Head slightly longer than broad, CI 98. Metapleural lobes large, conspicuous in absolute profile. Anterior half of propodeal dorsum shallowly concave, posterior half rising and shallowly convex. Petiole node in profile with an elongate, almost flat dorsum. Postpetiole broader than long in dorsal view.

Sculpture in the two species is very similar and they also share the characters of lacking a semicircular clypeal impression and possessing a broad ventral process on the peduncle of the petiole. Five other known species do not have a semicircular impression in the middle of the anterior clypeal margin, Ocymyrmex cavatodorsatus, Ocymyrmex velox, Ocymyrmex ankhu, Ocymyrmex zekhem and Ocymyrmex turneri, but none of these has the strongly developed constriction of the first gastral tergite seen in laticeps and cursor, and all lack a subpetiolar process. Apart from this turner; is small (HW < 1.30) and has large eyes which break the outline of the sides in full-face view; velox has a high, strongly convex petiole node and very feeble cephalic sculpture; and cavatodorsatus has the alitrunk strongly saddle-shaped in profile and the posterior half of the cephalic dorsum unsculptured.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Angola (type locality).


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Little is known about the biology of this species but a few species of Ocymyrmex have been studied in some detail. From this we can form some ideas about the biology of the genus as a whole. The following is summarized from Bolton and Marsh (1989). More details can also be found on the Ocymyrmex genus page.

Arnold (1916) observed that Ocymyrmex species with which he was acquainted nested in the ground in hot arid areas. The nests themselves went very deep into the ground, usually in loose sandy soil, and had a crater-like entrance. The ants used their well-developed psammophores to carry soil particles excavated from the nests. Recently both Marsh and Robertson (pers. comm.) have observed that workers of Ocymyrmex fortior close the nest entrance with small stones during periods of nest inactivity. Also, in Zimbabwe, fortior workers have been seen adding small stones to the crater-like nest entrance that were picked up from the ground some distance away from the nest. Species are now known which nest in very rocky soil and the nests may extend through the bedrock itself, necessitating the use of a large crowbar to expose the nest-chambers (H. Robertson, pers. comm.). Careful excavations of nests in well-structured sandy soil by one of us (Marsh) have revealed a simple nest structure. For example, nests of foreli typically have one entrance that opens into a vertical tunnel which terminates in a broad chamber at a depth of about 30 cm. Other brood and food chambers branch off from the tunnel at various intermediate levels. In most nest excavations the ergatoid queen was discovered near the bottom of the nest. In very unstructured loose sand, such as in the dry river beds of the Namib Desert, the tunnels and chambers of Ocymyrmex nests followed the root systems of shrubs and trees, and the major tunnel was therefore not necessarily vertical. Colonies of Ocymyrmex range in size from 200 to 1000 individuals (Marsh, 1987).

Other general aspects of their biology include workers that move rapidly, erratically, and are often active during the hottest part of the day. Specifics of their diet seem to vary by species but can include seeds and insects. For most species where queens are known they are worker-like ergatiod forms that are nonetheless clearly a morphologically distinct caste, as opposed to many intercaste ergatiods known from other genera that are intermediate between workers and more robust queens. Males of Ocymyrmex are often collected at lights but males associated with conspecific workers and females have rarely been collected.

Castes

Known only from the worker caste.

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • cursor. Ocymyrmex cursor Bolton, 1981b: 267 (w.) ANGOLA.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Holotype. TL 9.7, HL 2.08, HW 2.04, CI 98, SL 1.94, SI 95, PW 1.30, AL 2.74.

Anterior clypeal margin with a minute and very shallow inconspicuous indentation in the apron medially, without a conspicuous semicircular impression flanked by a pair of teeth. With the head in full-face view the occipital margin very shallowly but quite broadly concave. Maximum diameter of eye 0.44, about 0.22 x HW. Promesonotum in profile evenly rounded, sloping posteriorly. Anterior half of propodeal dorsum very feebly concave but above the spiracle very shallowly convex before rounding broadly and evenly into the declivity. Metapleural lobes prominent and narrowly rounded, easily visible in profile, not concealed by the bulge of the metapleural glands. Peduncle of petiole with a broadly triangular low blunt process on its ventral surface, about half-way between the insertion and the level of the spiracle. Node of petiole in profile low and broadly rounded, with a differentiated dorsal surface which is almost flat. In dorsal view the petiole node as long as broad, the postpetiole broader than long. Base of first gastral tergite constricted, forming a neck in dorsal view. Dorsum of head costulate, predominantly longitudinally so but with a few arching in over the eye. Ground-sculpture a fine superficial granulation or punctulation which is more conspicuous away from the midline of the head. Centre of pronotal dorsum almost smooth, with only vestigial sculpture; in front of this arched-transverse costulae are present and behind it longitudinal costulae run back between the mesothoracic spiracles. Remainder of dorsal alitrunk and propodeal declivity transversely rugose. Sides of alitrunk densely and evenly costulate-rugose, the sculpture regular except around the propodeal spiracle. Petiole ventrally transversely rugose from the level of the process and the peduncle dorsally with a few weak transverse rugae. The node itself more weakly sculptured, mostly with superficial patterning only but the posterior face with a few weak transverse rugulae. Postpetiole only with superficial patterning. Dorsal surfaces of head and alitrunk with numerous hairs of varying length but first gastral tergite only with scattered short hairs. Alitrunk glossy dull red, the head lighter and with an orange tint, the gaster darker, reddish brown.

Type Material

Holotype worker, Angola: Kopeio, vii.1931 (T. D. A. Cockerell) (The Natural History Museum).

References